It has been early appreciated that a metal substrate can be electroplated by use of a cylindrical electrode. For example in British Patent Specification No. 14,091 A.D. 1909, it is shown to plate a cathode strip outside an electrolyte tank, the strip being in contact with a rotating cylinder. The cylinder is made anodic and bears a porous, electrically nonconductive covering material that is filled with electrolyte. The rotating cylinder can have the porous covering continuously wet, as by partial immersion in a tank of electrolyte and the electrolyte can thereby wet the strip of material to be electroplated.
It may also be possible to use combination methods of applying electrolyte. Thus, for example, it has been shown in German Patent Publication No. 2,020,139 that a spray nozzle can impinge electrolyte at the zone of a roll and a moving work piece. Such roll may likewise be partially immersed in a bath of electrolyte. As also shown in this publication, the electrolyte may be internally fed to the cylinder, as by a central shaft, and then through radial tubes to wet outer porous plugs.
It has even been proposed that a central feed of electrolyte be pumped at sufficient velocity to provide for rotation of a cylindrical anode. For example, in British Pat. No. 493,108 electrolyte feed from a central spindle through a vaned cavity can provide for rotation of the cylinder. The cylinder, being notched, permits for a flow of electrolyte through the cylinder to an outer porous pad covering.
It has been proposed to prepare a suitable mesh covering for an anode roll from resin such as polyethylene, polypropylene, and polymerized vinyl halides, e.g., polyvinylchloride. For example in U.S. Pat. No. 4,441,975 such mesh layers for an anode roll have been noted. The mesh layer can be snugly fit to the roll by fixedly securing the mesh thereto. Such a roll may be non-sacrificial and can be of bimetallic construction, e.g., an inner layer for strength such as of steel and an outer, electrolyte-resistant conductive layer such as of zinc.
It would nevertheless be most desirable to provide a roll plating operation having extended and efficient operation. The operation should allow for plating at high current densities, yielding a smooth and even deposit. Furthermore this should desirably be coupled with flexible processing allowing for fast application of carefully controlled electroplate composition. Flexibility could desirably include retrofitting to existing coil paint lines where, working with existing space limitations, users could switch from plating to painting with ease of changeover.